U.S. Pat. No. 3,776,865 to Glaser and Lovald discloses polyamide resins obtained by reacting an acid component comprised of a polymeric fat acid and another dicarboxylic acid with an amine component comprising isophorone diamine or mixtures thereof with an alkylene diamine. At least 12.5 carboxyl equivalent percent of the polymeric fat acid is employed. The patentees disclose that these resins are useful as binders applied by aqueous systems, particularly in flexographic/gravure inks where water reducibility is desired.
U.S. Pat. No. 4,051,087 to Scoggins et al describes copolyamide resins useful as hot melt adhesives, molding resins, coatings or films. These are achieved through the use of substantially requivalent amounts of carboxyl and amine, i.e. a 1:1 ratio, proving essentially neutral resins. Only a slight excess, up to 5 mol percent of carboxyl or amine may be present. Examples I, II, III and V employed a polymeric (dimeric) fat acid, while Example IV employed azelaic acid in the absence of the dimer acid. The Example IV product is indicated as inferior to the polyamide employing the dimeric fat acid.
U.S. Pat. No. 3,781,234 to Drawert et al is another patent describing polymeric fat acids polyamides useful as hot melt adhesives. Approximately stoichiometric amounts of amine (ethylene diamine) and a carboxyl are employed, providing essentially neutral polyamides, neither acid value or amine value substantially exceeding the other. A copolymerizing C.sub.19 acid, heptadecane dicarboxylic acid is required along with the dimerized fatty acid.
U.S. Pat. No. 4,055,525 to Cheng describes a polyamide again useful as a hot melt adhesive. Substantially equivalent amounts of amine (hexamethylene diamine) and carboxyl are employed, so that a neutral polymer is provided. The acid component is comprised of a C.sub.19 diacid in admixture with another aliphatic dicarboxylic acid containing 5-10 carbon atoms.
Polyamide resins prepared from dimeric and/or higher polymeric fatty acids for use in flexographic/gravure inks are dissolved in volatile organic solvents, such as the lower alkanols. Environmental concern over the amounts of volatile organic solvents in the atmosphere has led to a desire to use aqueous solutions that have less volatile organic solvents contained therein. In order to accommodate the reduced levels of volatile organic solvents, the polyamide resins used as binders in flexographic/gravure inks should have increased water solubility and yet retain the other desirable properties of polyamide resins, based on polymeric fat acids.